I'm interested in what results you have been getting since you posted this last Dec, Seacam recommends 60 PVL,checking the Seacam home site they recommend the 70m PVL? I recently upgrades to a Seacam full frame(Nikon D3/D3X) and have both the 14-24mm and the 16-35mm and am trying to decide which to use. Also recently introduced is the Nikon 18-35mm which looks interesting.

I'm interested in what results you have been getting since you posted this last Dec, Seacam recommends 60 PVL,checking the Seacam home site they recommend the 70m PVL? I recently upgrades to a Seacam full frame(Nikon D3/D3X) and have both the 14-24mm and the 16-35mm and am trying to decide which to use. Also recently introduced is the Nikon 18-35mm which looks interesting.

I don't know the precise answer to this one as I'm a Canon user myself but the following may help you to understand the problem. As a zoom changes its focal length its optical configuration also changes. So the 'best' adjustment for dome to lens extension will depend on the focal legth set. For a zoom lens the answer is a compromise. Many (myself included) would suggest that the dome is set up for the zoom set at its shortest focal length as this is where it is likely to be used most - but this may lead to maladjustment at its longest focal length. So a midway setting may be a better compromise. This goes for all dome/zoom set ups. In my experience a 5mm extension shift doesn't do a vast amount, 10mm might start to show. Lastly, full frame will probably be more intolerant of maladjustment.....

Paul Kay, Thanks for the post. I'm well aware of the technical theory of the zoom lens and finding the "best" solution you mention. I guess my solution is to get the test charts out along with the various Seacam pvl extention rings and lens and do some tests until I happy. I also have an assortment of fixed focal length primes I may resort to for a project later in the year.

I guess my solution is to get the test charts out along with the various Seacam pvl extention rings and lens and do some tests until I happy. I also have an assortment of fixed focal length primes I may resort to for a project later in the year.

That's what I've done - I've found Seacam's recommendations to be pretty good on fixed focals but zooms are always going to be dependant on the user's preferences for their use I guess.

It is my understanding that Seacam has two variations of their Superdome, one of which is more of the full hemisphere. My Superdome is the older, less of a hemisphere, variation. I have been reasonably pleased with the results I've gotten using my Superdome with 80mm of extension tubes when shooting with Nikon's 16-35mm f4 lens.

It is my understanding that Seacam has two variations of their Superdome, one of which is more of the full hemisphere. My Superdome is the older, less of a hemisphere, variation. I have been reasonably pleased with the results I've gotten using my Superdome with 80mm of extension tubes when shooting with Nikon's 16-35mm f5 lens.

Fred

I may just be wrong but I doubt that this is the case. I have had Seacam remove the glass from a Superdome with the older, finer, thread mount used on its older housings, and put it into a new current fit mount where it looked just like the current version. So I very much doubt that there have been different Superdomes. Can you post a pic of yours by any chance?

As a seacam dealer you probably know more that I do about their products. I thought that I had read somewhere that Seacam had made a version of their superdome that was more of the full hemisphere. Maybe it was only the "deepwater" superdome that others on Wetpixel have referred to. My superdomes were purchased about 1999 or 2000. If all superdomes are the same portion of the full hemisphere, my good results using 80mm of extension tube with the 16-35mm lens would also be applicable for all seacam users and their superdomes.

One thing different on my superdomes is that they do not have the original seacam dome port shade of that era because it did not allow you to turn the housing on its nose to change film without the glass hitting the table or bench. So I made paira of concentric "nesting" shades for my superdomes. The inner shade is for use with a fisheye lens and does allow you to set the housing on its nose without bumping the glass. The second outer shade protrudes a bit farther and was cut to match the coverage of a 14mm lens. This shade is what I use slightly narrower angle coverage 17-35mm f2.8 and 16-35mm f4 lenses. The "larger" shade provided far better prevention of flare, particularly with the early versions of Sigma's 14mm lens which was all Nikon users had available prior to the introduction of the Nikon 14mm several years later. The outer shade can be easily removed when using the fisheye. Having them "nest" was the best way I could think of to travel with two shades. I also made pairs of nesting shades for my seacam wideports. The wider shade to use with the 17-35mm when I didn't want the size and bulk of the superdome and the outer shade cut for use with the Nikon 24-85mm.

Fred

As an afterthought - Harald Hordosch could answer this question about superdomes in a moment, and from what Stephen Frink has told me, he does watch for online comments about seacam products. But for some reason, he refuses to help in these discussions.